1. Field of the Invention
This invention generally relates to a semiconductor package and packaging method thereof, and more particularly, to an image sensor package and a packaging method for the same.
2. Description of the Related Art
In a conventional solid-state image device, as disclosed in Japanese patent publication number 61-134187 and entitled “Solid-State Image Pickup Device” as shown in FIG. 1, a CCD image sensing chip 303 is attached to a substrate 301 by means of an adhesive 302 and the substrate 301 has erected side walls 305 at its surroundings. A frame 307 for carrying a lens element 308 is fixed on the side walls 305 by means of an adhesive 306. However, in an actual packaging process, when the CCD image sensing chip 303 is attached to the substrate 301 by means of the adhesive 302, a positional error of the CCD image sensing chip 303 may be introduced such that the central axis 303c of the chip 303 may deviate from a predetermined central line 300c, i.e. de-center caused by the die attachment process. In addition, when fixing the frame 307 with the adhesive 306, a second positional error may be introduced such that the central axis 308c of the lens element 308 may deviate from the predetermined central line 300c to cause further de-center. In the solid-state image device 300, the positional deviation between the central axis 303c of the CCD image sensing chip 303 and the central axis 308c of the lens element 308 is preferably controlled within 20 micrometers such that the imaging beams from the lens element 308 can fall onto the effective sensing region of the CCD image sensing chip 303 and the captured image can be fully displayed without the shading phenomenon.
In order to solve the aforementioned misalignment problem, many methods have been provided in the art to decrease the occurrence of de-center, as disclosed in Japanese patent publication number 9-232548 and entitled “Solid-State Image Pickup Device” as shown in FIG. 2. In this reference, a plurality of stepped positioning portions 4, 5 and 6 are formed on a single supporting member 2 and then a solid-state image device 7, a lens element 8 and a diaphragm plate 9 are sequentially mounted on those positioning portions so as to improve positioning accuracy during packaging and decrease the occurrence of de-center. However, in an actual packaging process, manufacturing errors still exist for the positioning portions 4 of the solid-state image device 7 and the positioning portions 5 of the lens element 8. The accumulations of the manufacturing errors of the positioning portions 4 and 5 can still affect positioning accuracies of each element and introduce de-center. In addition, in this solid-state image pickup device, the supporting member 2 is directly formed on the leadframe 3 and thus the device is only applicable to a solid-state image device with a low pin count. As to a solid-state image device with a high pin count, the leadframe 3 cannot fulfill its requirement and therefore it is necessary to use the chip on board (COB) package. However, the supporting member 2 of the solid-state image device cannot be formed directly on the substrate.
According to the above reasons, it is necessary to further improve the above mentioned solid-state image device so as to solve the problem of positional deviation between the lens element and the chip in a COB-type image sensor package.